From owner-freebsd-questions@FreeBSD.ORG Thu Jul 15 18:55:28 2004 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 425C016A4F4 for ; Thu, 15 Jul 2004 18:55:28 +0000 (GMT) Received: from out011.verizon.net (out011pub.verizon.net [206.46.170.135]) by mx1.FreeBSD.org (Postfix) with ESMTP id D381043D2D for ; Thu, 15 Jul 2004 18:55:27 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from [192.168.1.3] ([68.161.84.3]) by out011.verizon.net (InterMail vM.5.01.06.06 201-253-122-130-106-20030910) with ESMTP id <20040715185527.OBXK18566.out011.verizon.net@[192.168.1.3]>; Thu, 15 Jul 2004 13:55:27 -0500 Message-ID: <40F6D317.1030406@mac.com> Date: Thu, 15 Jul 2004 14:55:19 -0400 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.1) Gecko/20040707 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Danny MacMillan References: <20040713200422.36735.qmail@web52502.mail.yahoo.com> <001001c46920$f347b790$152a15ac@spud> <20040714094104.GA71531@happy-idiot-talk.infracaninophile.co.uk> <20040714224010.GA1520@procyon.nekulturny.org> <20040714230638.0667d90c@localhost> <20040714232113.6bfba8e8@localhost> <20040715180514.GB1473@procyon.nekulturny.org> In-Reply-To: <20040715180514.GB1473@procyon.nekulturny.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Authentication-Info: Submitted using SMTP AUTH at out011.verizon.net from [68.161.84.3] at Thu, 15 Jul 2004 13:55:26 -0500 cc: freebsd-questions@freebsd.org Subject: Re: Freebsd 5.1 <-> Win XP Networking problems X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Jul 2004 18:55:28 -0000 Danny MacMillan wrote: [ ... ] > I'm pretty sure I understand subnet masks. The information I > was looking for was how my machine determines which MAC address > to put on the ethernet packet when sending to a machine off > my network. The packet will contain the MAC address of the router. Your machine will lookup the MAC address by doing an ARPOP_REQUEST for the IP address mentioned in the routing table which matches the destination IP address of the packet being sent (typically, using your "default" route). > First it has to know the machine is off my network, > and the network address (as determined by the IP address ANDed > with the subnet mask) is the only way I can figure that would > tell my computer that. In fact, if I understand correctly, > that is the raison d'etre of subnet masks. But nothing I read > about subnet masks comes out and says that directly. Your description is right. A good primer of TCP networking ought to discuss why people use subnetting, perhaps check 'TCP/IP Network Admin' from O'Reilly. -- -Chuck